Project: Nath’s 125

I’ve made a start on my mechanic-ing.

I went and got Nathan’s dead heap.

It’s seen better days.


I say I got his heap, that was a challenge in itself. How do you get a full motorbike into the back of a Mini?

Not easy.


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Which then fits neatly into said Mini.

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But, after breaking my back, it’s still a pile of broken bits.

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I sorted my shed out to look like this:


The bike was as dead as a very dead dodo, so I couldn’t just strip the engine down, as there would have been no way of knowing if I’d rebuilt it right.

I had to put everything back together and try to get the bike running before I could take it all apart and play.


That’s with the bike strapped onto the jack thing. I had to ratchet strap it on as there are no forks on it as they are totally smashed.

It’s been horrendous. The engine is quite light, as engines go, but it fits in the frame really awkwardly, and you have to hold it in position with one hand and a knee as you try and fit a bolt through the holes to support it. Then I went around fastening all the connectors and wires. They build them with oddly shaped connectors so they can only fasten to the corresponding odd shape so you can’t get it wrong. But when I’d rebuilt it there were two loose wires, no battery, and an odd shaped connector with no mate. I had the tank off a few times, searching for ages, I just couldn’t find it. The workshop manual is black and white pictures with no “what the hell is this bit?” section.

I gave up for the moment and decided to fix the bent side stand cut off switch I’d noticed while stripping it. Where’s the side stand?

Ah. It’s attached to the foot pegs (which were so badly bent I’d left them.) I went and got them and there was my blue connector! YAY!


The battery arrived today so I fitted that as well. The barrel on the ignition seems smashed so I took that off and ordered a new one. Happily the electrical bits come out as a separate unit, so you just have to change the barrel, no need to solder in new wires. I had a play with the remaining unit and reckoned I could operate the on/off switch without the barrel for now, but still no electrics at all.

I found and changed the main fuse. Nothing. Realised the starter relay was missing a cable, attached that properly. Nothing. I took the smashed headlight apart and realised two connections were undone. I traced them back and it was the ignition. I reconnected them, messed with the ignition electrical unit, and … LIGHTS!

I gave the starter a few blasts and got the engine turning over, I checked and I’ve got tons of spark at the plug!

I’m such a happy bunny! I’ve not got it started yet, but I’ve got a solid plan of attack. While it was just sat there, dead, I was feeling a bit overwhelmed. Now I’ve got lights, horn, starter motor, spark at the plug etc, it’s feels like it’s just a matter of ironing out the petrol feed problem.

I’m ordering the tools I need as I need them. They are surprisingly cheap. £12 for a compression test thing, (the very first test, according to my yank mechanic guru) £7 for a multimeter (tests all your electrics). I’ve had to watch videos on how to use a multimeter, I’ve no idea, but once I’ve got the hang of it I’ll be able to work out logically and definitively the source of any electrical problem. No more prodding wires and hoping for the best.

The next time in the shed I followed the fault finding chart. I used the compression tester (tons of compression) and the petrol pump pressure tester (zero pressure. Ah. Houston, we have a problem.) I used the multimeter to check there was voltage through the petrol pump circuit (yes) and that the lead to the ECU (the computer brain of the bike) was unbroken (all good) then I removed the pump from inside of the tank, squeezed out the filter and checked all the connection were good. I replaced the pump, tried to do a pump pressure test again, but there was so much pressure it squirted out! Sorted.

Tried it and


I was going to test my valve clearances then, as a bit of a dry run for my proper bike. Yamaha have made it too easy to be any good though. Inspection covers? An adjuster, instead of having to lift the cams off? For shame, Mr Yamaha. However, as soon as I started I realised Mr Yamaha was just teasing me.

An 8mm bolt recessed into the engine cooling fins. Upon which you can just get a spanner, but not turn it, and it’s too far recessed behind the fins to use a socket. And my long reach socket set only goes down to 10mm. Super.


I’ve ordered an 8mm, long reach socket.


The next session some of the bits I’d ordered had arrived.

I fitted the new ignition lock (had to snip the wires, fit new connectors and find the right wires as they were coloured wrong. They had black, black and white, red and brown. The ones on the bike were black, black and white, green and red. But black and white didn’t correspond to black and white. Of course not. Where would be the fun in that?)


Then set about trying to fit the new forks. I wasn’t sure they were going to fit as they were a cheap generic Chinese copy set, and I thought they might only be for the other model of this bike. They fitted, but the top and bottom yokes that hold them were out of line.


The screwdriver illustrates the where the bottom yoke was pointing, smack into the side of the top yoke.

I stripped the headstock to check for damage.


And refitted. It was still out of line. I managed to force one fork in. Then I realised the bottom yoke was a bit bent (from the crash) which was why I was still struggling. I tried to gently persuade it back into position (with a hammer and a cold chisel). I got the fork in, but when I fitted the pinch bolt the bottom yoke was too bent and it just stripped my thread.


I’ve ordered a used bottom yoke. I’ll have to take the forks out and strip the headstock right down to replace it, but that should mean the front end is fixed then.

It’s starting to look like a motorbike now though.


And the brakes fitted straight into the holes on the fork leg, so it is definitely the right forks.

I’ve ordered a cheap headlight, and as I was finishing up Wendy told me some parcels have arrived, so I’ve got the brake and clutch levers, gear change lever, and the faux induction pod thing for the smashed off space on the front right of the engine space in the last picture.

I forgot to say, as I’m trying to spend as little as possible to get this back on the road, I took the badly dented tank off, drained it, took the pump out, then pushed a lump of hard wood through the hole and started to beat the dents out. There are some hard to reach creases in the metal that I’m scared could split, but a guy on youtube showed a trick, where you inflate a motorbike tyre in the tank and gently pop it back out into shape. It’s worth a go.

I didn’t take a specific “before” picture so I’ve had to edit this one out of a full picture, hence the low quality.


After my first attempt at panel beating.


I’ll try the inner tube trick next.

The tank is ongoing. The inner tube, predictably, popped. But it took some of the dent out.

I stripped the front end down, properly this time, clocks off, handlebars etc hung to the side.


Then fitted the new bottom yoke. This time the forks just slid in.


So that’s the front end sorted. I’ve ordered a headlight, then I’ll reroute all the electrics through that and attach the clocks and such. I’ve already fitted the new levers and that shiny pod thing.


Coming together nicely.

Then I looked again at the thing on Nathan’s V5 Logbook, “This vehicle has been salvaged because the estimated cost of commercial repair was more than value of the vehicle.”

Fair enough. But I thought I’d better see if If I have to do anything special to put it back on the road. I googled that phrase and it’s the technical wording for “written off.” Still not a surprise. But there are four categories of ‘written off’, the first two mean the vehicle can never go back on the road. The first means it’s so badly damaged it’s too dangerous to even sell the parts. WHAT? (As an aside, private sellers are under no obligation to inform you of insurance categories against the vehicle, which is nice.)

All that money I’ve spent on bits… Quick panic then I found out you can pay for an HPI check that tells you which category of write off it is. Nath’s is Cat C, repairable, but deemed too expensive to be worth paying for. But it can go back on the road.

I said I was here to learn. That was a huge thing to learn, after I’ve been buying vehicles for 37 years.


I’m currently learning about electrics. The hard way.

To swap the smashed headlight you have to disconnect basically the whole wiring loom (as it’s routed through the headlight) fit the headlight then reconnect everything.


To add to the variables I’ve fitted a new ignition lock which runs non standard coloured wires and I’m trying to fit new clocks as well.

I put it back together and tried it and only the right hand side switchgear was working. I had the parking light but no headlight, the starter motor but no indicators, some of the clocks lit up, others not. It was baffling.

I tried different wiring combinations, blew the fuse about 5 times, and still had nothing to the right switchgear.

I’ve had to learn how to read a schematic, then read the post on electricals on the Yank’s site, (he is awesome, despite his views). The trick seem to be to trace the power line from the battery then use the multimeter to check the voltage in and out of every junction.

It took me ages to get to that basic step. Once I’d worked out a process I soon tracked down there was voltage going into the headlight relay, but none coming out on one wire.

Crossed it to test

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And there was light!

I’ve got my headlight on dipped and high beam, and the horn. All that’s left is to replace the headlight relay, track down what’s wrong with my indicators (they have a relay, have I fried that as well, somehow?) and make sure I’ve got full power to the clocks.

I’m waiting until the tester light and relay get here to carry on.